Hybrid Drawings & Mosaic Imagery

Hybrid Drawings are a mixture between measured line drawings, rectified photography, and 3-D point clouds.

In broad terms, a hybrid drawing is any drawing that mixes and superimposes a variety of ideas, techniques or media into a new, meaningful image – something that architects & designers have long gravitated towards. The hybrid drawings that I create for historic preservation projects are special sub set of this general category because they are measured drawings.

Hybrid Drawings make dimensional accuracy the conjunction point between various digital media. When a line drawing – either as a projected elevation (in 2-D) or as a “wire frame” model (in 3-D) – accurately represents the real world size and shape of a surface, it can be superimposed over another description of the same surface in a different media. In my work these additional media include both rectified photographs (aka ortho-photos) and 3-D point clouds derived through photogrammetry and/or laser scanning.

Merging CAD delineation with rectified photography produces a hybrid drawing. These different types of description can occupy the same “space” because they each depict the same object or condition – albeit in different ways. The line-work establishes precise edges between vertices while the pixels describe material color and condition. In short, measured hybrid drawings integrate the quantitative description of vectors with the qualitative description of pixels.

When considering a hybrid drawing, one wonders: is it a photograph that behaves like a drawing (since it is scale-able) or is it a drawing that looks like a high quality photograph? The answer is yes!

The Virginia State Capitol

How are hybrid drawings delivered/shared?

Typically I deliver measured hybrid drawings in AutoCAD format in which the line-work is composed of AutoCAD vector entities and the raster imagery consists of JPG images that are referenced into the drawing. Often, the raster images are many (created from different vantage points) thereby creating a mosaic image of the subject.

HABS Standards have long dictated that good professional practice in documenting existing structures should include both measured drawings and photographs. Hybrid drawing techniques allow these two types of documentation to work together in a new and powerful way.

Mosaic Imagery

A powerful Mosaic Image is created when a number of “ortho-photos” are assembled together into an accurate line drawing in CAD format. This technique provides a way to create a photographic image that can “see around” columns, trees or other visual obstructions – allowing a surface to be viewed from multiple viewpoints simultaneously.

See also this blog post which discusses the difference between multiple point of view mosaic images (such as those shown on this page) and single point of view mosaic images, also known as panoramic images (sample below)

Panoramic image of Ledoux’s Royal Saltworks

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Telephone: 540 447 4405

About

Aaslestad Preservation Consulting, LLC provides architects, preservationists, and building owners with high quality documentation that describes the existing conditions of built structures - in photographs and/or in CAD format, as measured drawings, high density point clouds, accurate 3-D models...

Peter Aaslestad is recognized in the U.S. as a pioneer in using photogrammetry to record historic structures as a consulting service to other architects, preservationists and property owners.

Drawing on his background in architecture & photography, Peter has documented the existing conditions of wide variety of structures - including ruins, the homes of presidents, entire neighborhoods, national landmarks and more in the United States, Europe, and Asia.

His consulting service offerings for preservation & design work include 3D scanning, creation of high density point clouds & 3D models, orthophotography, rectified photography, hybrid drawings, mosaic imaging, and accurate measured drawings in CAD format. These can include elevations, plans, sections, reflected ceiling plans that capture an describe a building's envelope and/or its interior spaces and surfaces.

Mr. Aaslestad has been a guest lecturer for the APT (Association for Preservation Technology), Columbia University, and the Universities of Virginia, North Carolina and Florida. In 2001, Mr. Aaslestad became an active member of the investigative team working to restore James Madison’s Montpelier. The groundbreaking work produced by this team was recognized in 2003 with the prestigious Paul E. Buchanan Award, presented by the Vernacular Architecture Forum.

Peter also contracts creative work as a designer & as a free lance photographer with works appearing in a variety of publications over his 25 year career.